In concrete slab construction, the manual striking off of wet or plastic concrete is a labor intensive process that generally consists of three steps, the first of which will differ according to the desired elevation of the finished concrete surface. For example, if the finished surface is intended to parallel the base over which the concrete is being placed (thereby resulting in a slab of constant thickness), then the wet concrete surface at various small isolated spots is first struck off to its intended finished elevation by measuring up from the base using a gage stick equal in length to the desired finished slab thickness. If, however, the finished surface is not necessarily intended to be of constant thickness, but is instead intended merely to be planar, then the wet concrete surface at various small isolated spots is first struck off to its intended finished elevation by using an optical or laser level and grade stick to define the desired plane. In both of these above-described cases, the small isolated reference spots that are initially formed in the wet concrete surface are termed “wet pads”. To facilitate subsequent strike-off operations, the distances between adjacent wet pads are kept somewhat shorter than the length of the straightedge that is to be used to strike off the bulk of the concrete.
The second step in a manual strike-off operation involves using the straightedge and two adjacent wet pads as elevation references. The concrete between the wet pads is struck off to create a narrow, elongated section of at-grade concrete that is termed a “wet screed”. Again, to facilitate subsequent strike-off operations, the wet screeds are generally made to parallel one another at spacings somewhat shorter than the length of the straightedge.
The last step in a manual strike-off operation involves using the straightedge and two adjacent wet screeds as elevation references to strike off the concrete between the wet screeds to grade. However, owing to the plastic, unstable character of the wet pads and wet screeds that are used to control the elevation of the straightedge, the finished surfaces produced by this so-called “wet screed” method of concrete slab construction typically exhibit poor conformity to the desired grade.